Coupling Global and Regional Air Quality Models: Influence of Hemispheric Transport of Mineral Dust and Biomass Burning Aerosols on U.S. Air Quality

NOAA's Air Quality (AQ) prediction system uses the Community Multiscale Air Quality (CMAQ) model driven by meteorological fields from the NAM (North America Mesoscale Model). For this study, the lateral boundary conditions for CMAQ were provided by the NCEP Global Forecast System (GFS) linked to GOCART (Goddard Chemistry Aerosol Radiation and Transport Model) in developmental predictions for aerosols from dust and biomass burning events. Aerosols considered from biomass burning include hydrophilic/hydrophobic black carbon and organic carbon species. GOCART's 5 dust size bins are mapped to CMAQ's accumulation and coarse modes along the CMAQ lateral boundaries. Regional impacts on AQ prediction were evaluated over the U.S. The influence of external aerosol sources depends on multiple factors including: source strength, injection height, transport pathways, and intrusion altitude. Three scenarios are examined: summertime Saharan dust events, springtime Asian dust intrusion and biomass burning events. In most events, dust tends to enter North America in the altitudes lower than biomass burning aerosols due to their different emission injecting heights. For these scenarios, performance of the global model is evaluated to determine its influence on CMAQ performance. Statistical comparison of CMAQ aerosol predictions with surface AIRNOW measurements will be presented.